0
Proximity switches open or close an electrical circuit when they make contact with or come within a certain distance of an object. Proximity switches are most commonly used in manufacturing equipment, robotics, and security systems. There are four basic types of proximity switches: infrared, acoustic, capacitive, and inductive.
Infrared proximity switches work by sending out beams of invisible infrared light. A photodetector on the proximity switch detects any reflections of this light. These reflections allow infrared proximity switches to determine whether there is an object nearby. As proximity switches with just a light source and photodiode are susceptible to false readings due to background light, more complex switches modulate the transmitted light at a specific frequency and have receivers which only respond to that frequency. Even more complex proximity sensors are able to use the light reflected from an object to compute its distance from the sensor.
Acoustic proximity sensors are similar in principle to infrared models, but use sound instead of light. They use a transducer to transmit inaudible sound waves at various frequencies in a preset sequence, then measure the length of time the sound takes to hit a nearby object and return to a second transducer on the switch. Essentially, acoustic proximity sensors measure the time it takes for sound pulses to "echo" and use this measurement to calculate distance, just like sonar.
Capacitive proximity switches sense distance to objects by detecting changes in capacitance around it. A radio-frequency oscillator is connected to a metal plate. When the plate nears an object, the radio frequency changes, and the frequency detector sends a signal telling the switch to open or close. These proximity switches have the disadvantage of being more sensitive to objects that conduct electricity than to objects that do not.
Inductive proximity switches sense distance to objects by generating magnetic fields. They are similar in principle to metal detectors. A coil of wire is charged with electrical current, and an electronic circuit measures this current. If a metallic part gets close enough to the coil, the current will increase and the proximity switch will open or close accordingly. The chief disadvantage of inductive proximity switches is that they can only detect metallic objects.
Proximity switches are used in manufacturing processes -- for example, to measure the position of machine components. They are also used in security systems, in applications such as detecting the opening of a door, and in robotics, where they can monitor a robot or its components' nearness to objects and steer it accordingly
BY:ragith
Still curious? Ask our experts.
Chat with our AI personalities
Ross
Steve
CoachAdd your answer:
Earn +20 pts
How do automatic systems work?
An object disrupts or enters the proximity sensor zone beams out from a sensor tap. The infra red sensor detects the object and sends an electronic signal to the solenoid valve (usually inside a control box mounted under the sink) via its signal wire. The solenoid valve opens up to let water supply through it, and water is dispensed or fed to the user via the flexible hose connected to the tap itself. More info and visual diagram can be found here: http://www.autotaps.com/how-automatic-tap-work.html
How do coin operated machines work?
The weight of the coin pushes down on a sensor, and the sensor reads the amount of money put in. Or sometimes scanning the size of coins.
In my office lights turn on automatically when I enter the room how does it know that I am in the room?
Most likely the room has some sort of motion sensor to tell if someone is present. A heat sensor can tell if a person is in the room by the heat generated by the human body. A sound sensor can respond to noise made by a person walking, talking or otherwise. Either will work. The triggered sensor can turn on the lights or anything else electrically. The lights are usually attached to some kind of timer so that if no activity is detected in the room for a while, the lights are turned off until the next time the sensor is triggered.
What is found in a computer scanner?
They usually contain either a contact image sensor or a charge coupled device and a means to move the sensor or optics pointed at the sensor. There would also be a light source as well in the case of the CCD technology. Then there would be a circuit board to make sense of the signals and send it to the computer.
Is it wacom bamboo touch is only touch tablet or can use pen to?
It is a capacitive touchpad. It does not include, and would not work with the wacom pen. The pen uses an active sensor, which is not included in the touch model tablet. If you want to touch and use pen, then you need to buy the "pen and touch" model.
